The commission investigating reports of voter fraud in Afghanistan's
presidential election has thrown out votes from 83 polling stations.
The U.N.-backed Electoral Complaints Commission Thursday ordered to exclude ballots from 51 polling sites in Kandahar, 27 in Ghazni and five in Paktika. Those areas showed strong support for incumbent President Hamid Karzai.
The ECC did not say how many ballots were nullified.
In a statement explaining its decision, the ECC cited "clear and convincing evidence of fraud", including unfolded ballots, uniformity of markings and lists of voters with fictitious card numbers.
The commission has also ordered recounts at some polling locations.
Afghan President Hamid Karzai had earlier welcomed partial returns from the country's controversial August 20 presidential elections, which gave him 54 percent of the vote.
But his main challenger, former Foreign Minister Abdullah Abdullah, who has 28 percent of the vote, disputed those results.
His campaign said the results had been tallied in violation of election laws.
A U.S. election monitoring group called the National Democratic Institute expressed "deep concern" Thursday over the high number of fraud complaints that have been filed.
It said it found grounds for concern in a number of provinces, including Nuristan, Paktia, Helmand and Badghis. In these cases, many polling stations reported voter turnout that was far higher than analysts had estimated, prompting concerns about the poll's credibility.
The U.S. Embassy in Kabul has called for patience as the electoral process continues.
The Obama administration has said that a "legitimate" election process is vital to the future of U.S.-Afghan relations.
A credible election is also deemed crucial to the reputation of the international mission to fight the Taliban, and preserve Afghanistan's fledgling democracy.
Some information for this report was provided by AFP and AP.